let lessons = [
	{title: '媒体查询响应式布局',category: 'css'},
  {title: 'FLEX 弹性盒模型',category: 'css'},
	{title: 'MYSQL多表查询随意操作',category: 'mysql'}
];

for(let item of lessons) {
	console.log(item)
}

var it = lessons.entries()
console.log(it, typeof it, it.constructor)
console.log(Object.prototype.toString.call(it))  // [object Array Iterator]



var item = it.next()
console.log(item.done, item.value, item)
console.log('-----------------------\n')


var item = it.next()
console.log(item.done, item.value)

var item = it.next()
console.log(item.done, item.value)

var item = it.next()
console.log(item.done, item.value)

